Method for making and evaluating a sample cut

ABSTRACT

In a method for making and evaluating a sample cut in an engraving machine, an engraving control signal for guiding a stylus is formed from engraving data. The stylus cuts a series of cups. During a trial engraving trial cups are engraved and a video image is made. In accordance with screen parameters, measuring points are fixed in the video image as distances to a selected reference point. Geometric parameters of the trail cups are measured in the video image and are compared to corresponding geometric parameters of the cups representing predetermined tone values. Adjustment values are deduced from this comparison which are used to calibrate the engraving control signal.

BACKGROUND OF THE INVENTION

The invention is in the field of electronic reproduction technology andis directed to a method for producing and evaluating a sample cut in anelectronic engraving machine for engraving printing forms, particularlyprinting cylinders, for rotogravure.

In an electronic engraving machine, an engraving element with anengraving stylus as a cutting tool moves in an axial direction along arotating printing cylinder. The engraving stylus controlled by anengraving control signal cuts a sequence of depressions, called cups,arranged in an engraving raster into the generated surface of theprinting cylinder. The engraving control signal is formed in anengraving amplifier by superimposition of image signal values thatrepresent the gradations between “light” (white) and “dark” (block) tobe engraved with a periodic raster signal (vibration). Whereas theraster signal effects a vibrating lifting motion of the engraving stylusfor generating the engraving raster, the image signal values determinethe geometrical dimensions of the cups engraved into the generatedsurface of the printing cylinder.

So that the cups engraved when engraving the printing form correspond tothe gradations prescribed by the image signal values, the engravingcontrol signal must be calibrated. For that purpose, sample cups forpredetermined gradations are engraved before the engraving of theprinting form with what is referred to as a sample cut, for example forthe gradations “light” and “dark”. After the sample cut, the actualgeometric dimensions of the engraved sample cups are identified andcompared to the rated geometrical dimensions of those cups thatrepresent the gradations prescribed for the sample engraving. Settingvalues, for example, for the parameters “light”, “dark”, and“vibration”, are acquired from the comparison of the geometricdimensions, the engraving amplifier being calibrated with these suchthat the cups in fact produced in the later engraving correspond to thecups required for a gradation-correct engraving.

After the sample cut, the actual geometric dimensions of the engravedsample cups, for example the transverse diagonals, the longitudinaldiagonals, the widths of the penetration and the web widths must beidentified. Of the actual geometrical dimensions ensues by measuring thesample cups with a

Earlier, the determination of the actual geometrical dimensions ensuedby measuring the sample cups with a measuring microscope put in place onthe printing cylinder and having an integrated scale.

WO-A-9 419 900 already discloses a method wherein the actual geometricaldimensions of the engraved sample cups are measured in a video imageregistered with a video camera.

In practice, the demand for a more exact evaluation of the video imageof the sample cups is present in order to improve the engraving quality.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to improve a methodfor producing and evaluating a sample cut in an electronic engravingmachine for engraving printing forms, particularly printing cylinders,for rotogravure such that an automated, exact determination of theactual geometric dimensions of the engraved sample cups is assured.

According to the method of the present invention for producing andevaluating a sample cut in an electronic engraving machine for engravingprinting forms for rotogravure, an engraving control signal is formedfor driving the engraving stylus of an engraving element from engravingdata which represent rated gradations between “light” and “dark” to beengraved and from a periodic raster signal for generating an engravingraster. With the engraving stylus, a sequence of cups arranged in theengraving raster are engraved engraving line by engraving line into theprinting cylinder, geometric parameters of the cups defining engraved,actual gradations. With the engraving element, implementing a feedmotion directed in an axial direction of the printing cylinder forplanar engraving of the printing cylinder. A sample engraving occurringbefore actual engraving of the printing form is provided wherein samplecups are engraved for predetermined rated gradations. The video image ofthe sample cups engraved in the sample engraving is produced. Formeasuring geometric parameters of the engraved sample cups, selecting anengraved sample cup in the video image for one of the predeterminedrated gradations as a reference location in an XY-measuring systemallocated to the video image. Dependent on the raster parameters of theengraving raster, measuring locations for measuring the geometricparameters of the specimen cups in the video image are defined ascoordinate-related spacings from the selected reference location. Thegeometric parameters of the specimen cups at the determined measuringlocations are measured by interpreting the video image and comprisingthem to the geometric parameters that define the predetermined ratedgradations. Setting values are derived from the comparison with whichthe engraving control signal is calibrated such that the engraved actualgradations correspond to the rated gradations to be engraved.

The invention is explained in greater detail below with reference toFIGS. 1 through 9.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic exemplary embodiment of an electronic engravingmachine for engraving printing forms;

FIG. 2 is a video image of engraved sample cups;

FIG. 3 a shows the formation of a measuring band comprising a measuringline;

FIG. 3 b shows the formation of a measuring band comprising threemeasuring lines;

FIG. 4 is a graphic presentation directed to the automatic determinationof a measuring distance within a measuring band;

FIG. 5 is a graphic illustration directed to the measurement of thetransverse diagonal of a sample cup;

FIG. 6 is a graphic illustration directed to the measurement of thelongitudinal diagonal of a sample cup;

FIG. 7 is a graphic illustration directed to the measurement of thepuncture width of two sample cups;

FIG. 8 is a graphic illustration directed to the measurement of the webwidth of two sample cups; and

FIG. 9 is a video image of engraved sample cups with measuring surfacesaround the sample cups.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a schematic exemplary embodiment of an electronic engravingmachine for engraving printing forms for rotogravure. For example, theengraving machine is a HelioKlischograph® of Hell Gravure Systems GmbH,Kiel, Del.

A printing cylinder 1 is rotationally driven by a cylinder drive 2. Theengraving on the printing cylinder 1 occurs with an engraving element 3that, for example, is designed as an electromagnetic engraving elementhaving an engraving stylus 4 as a cutting tool.

The engraving element 3 is located on an engraving carriage 5 that canbe moved in the axial direction of the printing cylinder by an engravingcarriage drive 7 with a spindle 6.

The engraving stylus 4 of the engraving element 3 cuts a sequence ofcups arranged in an engraving raster into the generated surface of therotating printing cylinder 1 engraving line by engraving line whileengraving carriage 5 with the engraving element 3 moves along theprinting cylinder 1 in the feed direction.

In the illustrated exemplary embodiment, the engraving of the cupsoccurs on individual engraving lines proceeding circularly in thecircumferential direction around the printing cylinder (1), whereby theengraving carriage (5) implements an axial feed step to the nextengraving line after the respective engraving of the cups of oneengraving Line. Such an engraving method is disclosed, for example, inU.S. Pat. No. 4,013,829. Alternatively, the engraving can also occur inan engraving line helically proceeding around the printing cylinder 1,whereby the engraving carriage 5 then implements a continuous feedmotion during engraving.

The engraving stylus 4 of the engraving element 3 is controlled by anengraving control signal (GS). The engraving control signal (GS) isformed in an engraving amplifier 8 by superimposition of a periodicraster signal (R) with image signal values (B) that represent thegradations of the cups to be engraved between “light” (white) and “dark”(black). While the periodic raster signal (R) effects a vibratinglifting motion of the engraving stylus 4 for producing the engravingraster, the image signal values (B) determine the respective geometricdimensions of the engraved cups such as penetration depth, traversediagonal and longitudinal diagonal according to the image signal values(B).

The engraving raster is defined with respect to screen angle and screenwidth by the frequency of the raster signal (R), by the circumferentialspeed of the printing cylinder 1 and by the axial feed step width of theengraving element 3.

The analog image signal values (B) are acquired in a D/A converter 9from engraving data (GD) that are deposited in an engraving data memory10 and are read out therefrom engraving line by engraving line and aresupplied to the D/A converter 9. An engraving datum of at least one byteis allocated in the engraving raster to each engraving location for acup, this engraving datum containing, among other things, the gradationbetween “light” and “dark” to be engraved as engraving information,whereby, for example, the engraving datum GD=161 is allocated to thegradation “light” and the engraving datum GD=1 is allocated to thegradation “dark”.

An XY-coordinate system whose X-axis is oriented in the axial directionand whose Y-axis is oriented in the circumferential direction of theprinting cylinder 1 is allocated to the printing cylinder 1. Thex-location coordinates of the engraving locations on the printingcylinder 1 arranged in the engraving raster that define the axialpositions of the engraving stylus 4 of the engraving element 3 withreference to the printing cylinder 1 are generated by the engravingcarriage drive 7. A position sensor 11 mechanically coupled to thecylinder drive 2 generates the corresponding y-location coordinates thatdefine the relative circumferential positions of the rotating printingcylinder 1 relative to the engraving stylus 4 of the engraving element3. The location coordinates (x, y) of the engraving locations aresupplied to a controller 14 via lines 12, 13.

The controller 14 controls the addressing and the readout of theengraving data (GD) from the engraving data memory 10 dependent on thexy location coordinates of the current engraving locations via line 15.The controller 14 also generates the raster signal (R) on a line 16 withthe frequency required for generating the engraving raster, a controlcommand S₁ on a line 17 to the engraving carriage drive 7 for settingthe feed step width relevant for producing the engraving raster and forcontrolling the step-by-step feed of the engraving element 3 duringengraving and also generates a further control command (S₂) on a line 18to the cylinder drive 2 for setting the circumferential speed of theprinting cylinder 1 required for generating the engraving raster.

For implementation of a sample cut before the actual engraving of theprinting form, the engraving machine comprises a computer 19 thatsupplies the engraving data (GD*) required for engraving the sample cupsto the D/A converter 9. Each engraving datum (GD*) represents thepredetermined rated gradation of a sample cup or, respectively, thecorresponding rate geometrical value, for example the rated transferdiagonal or the rated longitudinal diagonal of the same cup.

For measuring the sample cups engraved in the sample cut, a measuringcarriage 20 displaceable in the axial direction of the printing cylinder1 and having a video camera 21 for registration of a video image of thesample cups and an image evaluation unit 23 connected to the videocamera 21 via a line 22, which can also be integrated in the videocamera, is provided for measuring the sample cups in the video image.The employment of a measuring carriage 20 is advantageous particularlygiven multi-channel engraving machines with which a plurality ofengraving lanes are engraved with a respective engraving element 3. Inthis case, a corresponding sample cut must be implemented and measuredfor each engraving lane. The measuring carriage 20 can be automaticallymoved to the required, axial measuring position in the individualengraving lanes via a spindle 24, being moved by a measuring carriagedrive 25. The measuring carriage drive 25 is controlled by a controlinstruction (S₃) on a line 26 proceeding from the controller 14.

Alternatively, the video camera 21 can also be arranged in the region ofthe engraving element 3, whereby the pickup of the video image canoccur, for example, via a light-conducting cable.

A configuration memory 27 supplies the prescriptions required forengraving and for measuring the sample cups via a line 28, supplyingthese to the computer 19, and via a line 29 to the image evaluation unit23. The measured results are transmitted as actual geometric values fromthe image evaluation unit 23 to the computer 19. In the computer 19,setting values for calibrating the engraving amplifier 8 are acquired bycomparing the predetermined rated geometric values and measured actualvalues, these being supplied to the engraving amplifier 8 via a line 31.The engraving amplifier 8 is then calibrated with the identified settingsuch that the cups actually generated in the later engraving of theprinting form correspond to the cups required for a gradation-correctengraving.

The calibration of the engraving amplifier 8 can occur automaticallybefore the engraving of the printing form or on line during theengraving of the printing form. The calibration of the engravingamplifier 8, however, can also be manually implemented in that theidentified setting values are merely indicated to the computer 19 thesethen being manually transferred onto the engraving amplifier 8.

For engraving the sample cups, the computer 19, for example, calls theengraving data (GD*) for the rated gradations “dark” (GD*−1), “light”(GD*=161) and for at least one “mid gradation” (GD*=80) between “light”and “dark”. The engraving data (GD*) that have been called are convertedinto the engraving control signal (GS) for the engraving element 3. Theengraving element 3 engraves at least one sample cup 33 for “light” (L),“dark” (T) and “mid gradation” (M) in the engraving raster on engravinglines 32 that lie side-by-side. Preferably, a plurality of identicalsample cups 33 are engraved on each engraving line 32, for example overa selectable engraving line region. When the web width is also to beidentified in addition to the transverse diagonals and the longitudinaldiagonals, sample cups 33 for “dark” must be engraved on at least twoengraving lines (32) lying next to one another. A corresponding samplecut must be implemented for each color separation or, respectively, foreach engraving raster, whereby the different parameters of the engravingraster such as screen angle and screen width are deposited in theconfiguration memory 27.

After the sample cut, the video camera 21 registers a video image of theengraved sample cups 33. The registration of the sample cups 33 canoccur given a stationary printing cylinder 1- or can occur with acorresponding synchronization given a rotating printing cylinder 1.

The measuring of the geometrical parameters of the engraved sample cups33 in the image evaluation unit 23 is explained in greater detail belowon the basis of the registered video image.

FIG. 2 shows a video image 35 of the engraved sample cups 33 registeredwith the video camera 21. The orthogonal engraving raster composed ofhorizontal and vertical raster lines is shown, whereby the verticalraster lines are the engraving lines 32. For example, engraved samplecups 33 for “light” (L), “dark” (T) and “mid gradation” (M) are shown onthree engraving lines 32 lying next to one another. The centers ofgravity of the sample cups 33 lie on the inner sections of the rasterlines of the engraving raster. In order to assure a dependableevaluation, the size of the video image 35 is selected such that atleast one complete sample cup 33 lies within the video image 35 for eachrated gradation.

The video image 35 is comprised of a plurality of pixels 36 whoseposition in the video image is defined by the location coordinates (x*,y*) of the XY measuring system, which is likewise aligned in axialdirection and in circumferential direction of the printing cylinder 1. Avideo datum (VD) of, for example, 8 bits that identifies the respectivegray scale value is allocated to each pixel 36, so that a total of 254gray scale values can be distinguished between “black” (VD=0) and“white” (VD=255). The gray scale value scan be reduced to two values byfiltering or with the thresholds such that, for example, those pixelsthat fall onto the generated surface of the printing cylinder 1 have thevideo datum VD=0 allocated to it and those pixels that lie on the areasof the sample cups 33 have the video datum VD=1 allocated to them. Thecontour (density discontinuity) of a cup surface is thereby identifiedby the switch of the video datum from “0” to “1” or from “1” to “0”.

For measuring the geometrical parameters of the specimen cups 33 in thevideo image 35, at least one measuring field displaceable over the videoimage 35 is defined. The measuring field is designed stripe-shaped inthe exemplary embodiment and is referred to below as measuring band 39whose longitudinal expanse is at least equal to the spacing of twoengraving lines from one another. The measuring of the specimen cups 33for “light”, “dark” and “mid gradation” can ensure successively with onemeasuring band 39 or can respectively ensure with a separate measuringband 39.

The measuring band 39 can be shifted to selectable measuring locations40 within the video image 35 and can be aligned in an arbitrarydirection with respect to the XY measuring system 37, whereby, forexample, the mid point of the measuring band 39 is defined as measuringlocation 40.

Before the sample engraving, one of the specimen cups 33 is selected asreference cup, the mid point thereof to be the reference location 41 forthe positioning of the measuring band 39 to the desired measuringlocation 40 within the video image 35. In a preferred way, the mid pointof a specimen cup 33 for a rated mid gradation (M) is selected asreference location 41.

The determination of the measuring location 40 for the measuring bands39 ensues by prescribing the coordinate-wise distances (Δx*, Δy*) fromthe reference location 41 dependent on the geometry of the engravingraster for each color separation. The reference location 41, thepredetermined spacings (Δx*, Δy*) from the reference location 41 and thedesired alignment of the measuring band 39 can be stored in theconfiguration memory 27.

Since the specimen cups 33 lie on the engraving lines 32, the spacing(Δx*, [sic]) of the measuring band 39 from the reference location 41 iseither 0 in X-direction, equal to the engraving line spacing or equal toa multiple of the engraving line spacing. The spacing (Δy*) from thereference location 41 in Y-direction, by contrast, is dependent on whatis to be measured.

For measuring the maximum transverse diagonal (d_(qmax)) or an arbitrarytransverse diagonal (d_(d)), i.e. the expanse of the cup area inX-direction (feed direction), the measuring band 39 has its longitudinalexpanse directed in X-direction. For measuring the maximum transversediagonal (d_(qmax)), the distance (Δy*) from the reference location 41in the Y-direction is either 0, equal to the screen width in Y-directionor a multiple of the screen width. For measuring an arbitrary transversediagonal (d_(q)), corresponding intermediate spacings from the referencelocation 41 in Y-direction are prescribed. The spacing (Δx*,) of themeasuring band 39 from the reference location 41 in the X-direction iseither 0, equal to the engraving line spacing or to a multiple of theengraving line spacing in both instances.

For measuring the maximum longitudinal diagonal (d_(Lmax)) or anarbitrary longitudinal diagonal (d_(L)), i.e. the expanse of the cuparea in Y-direction (circumferential direction), the measuring band 39is aligned with its longitudinal expanse in Y-direction. For measuringthe maximum longitudinal diagonal (d_(Lmax)), the spacing (Δx*) of themeasuring band 39 from the reference location 41 in the X-direction iseither 0, equal to the engraving line spacing or to a multiple of theengraving line spacing. For measuring an arbitrary longitudinal diagonal(d_(L)), corresponding intermediate spacings from the reference location41 are prescribed in the X-direction. The spacing (Δy*) from thereference location 41 in the Y-direction is either 0, equal to thescreen width in the Y-direction or to a multiple of the screen width inboth instances.

For measuring the puncture (d_(ds)), i.e. the width of the engravingchannel in the X-direction, which connects two cups engraved on anengraving line, the measuring band 39 has its longitudinal expanse againaligned in the X-direction. The spacing (Δx*) of the measuring band 39from the reference location 41 in the X-direction is again either 0,equal to the engraving line spacing or to a multiple of the engravingline spacing. The spacing (Δy*) from the reference location 41 in theY-direction is thereby either 0, equal to the screen width in theY-direction or to a multiple of the screen width.

For measuring the web width (d_(SB)), i.e. the width of the materialthat remains standing between two deep cups engraved on neighboringengraving lines, the measuring band 39 is expediently turned such thatit has its longitudinal expanse aligned approximately perpendicular tothe course of the web.

The measuring band 39 is composed of at least one measuring line 39′,preferably of a plurality of measuring lines 39′ proceeding parallel toone another, and each measuring line comprises a plurality of pixels 36whose spacing from one another represents a length increment. Bycounting the pixels 36 within a measuring distance, thus, the length ofthe measuring distance can be measured as a multiple of the lengthincrement.

FIG. 3 a shows the formation of a measuring band 39 that is composed ofa measuring lines line 39′ having fourteen pixels 36.

FIG. 3 b shows the formation of a measuring band 39 that is composed ofthree measuring lines 39′ proceeding parallel to one another and eachrespectively having fourteen pixels 36.

As already mentioned, the edges of a cup area, of a web or of a punctureform a contour in the registered video image 35. The measuring distancefor transverse diagonal, longitudinal diagonal, web width and puncturewidth thus derives from the respective distance of correspondingcontours from one another.

The end points of a measuring distance for transverse diagonal,longitudinal diagonal, web width and puncture width are advantageouslydetermined with the assistance of the measuring band 39 itself on thebasis of an automatic recognition of two neighboring contours, in thatthe video data (VD) of two respectively successive pixels 36 of ameasuring line 39 are examined for a contour transition.

FIG. 4 shows a measuring band 39 with a measuring line 39′ and twocontour lines 43 spaced from one another. The video data (VD) allocatedto the individual pixels 36 are also shown, whereby the contour lines 43are identified by the transition “0” to “1” and “1” to “0”. On the basisof an automatic contour recognition, the end points of the measuringdistance 44 are determined, this being eight pixels 36 long in theillustrated case.

The sequence in which the video data (VD) of neighboring pixels 36 areexamined for automatic contour recognition is dependent on what is to bemeasured. In the measurement of the transverse diagonal (d_(Q)) or ofthe longitudinal diagonal (d_(L)), the video data (VD) are expedientlyexamined proceeding from the middle of a measuring line 39′, i.e. fromthe middle toward the edges of a cup area.

Given measurement of the puncture width (d_(DS)) or of the web width(d_(SB)) by contrast, it proves advantageous to examine the video data(VD) from the end points of a measuring line 39′ toward the middle.

FIG. 5 shows the measurement of the maximum transverse diagonal(_(Qmax)) of a sample cup 33 with the measuring band 39 directed inX-direction, whereby the end points of the measuring distance 44 aredefined by the contours 43 of the sample cup 33.

FIG. 6 shows the measurement of the maximum longitudinal diagonal(d_(Lmax)) of a sample cup 33 with the measuring band 39 directed in theY-direction.

FIG. 7 shows the measurement of the puncture width (d_(DS)) of twosample cups 33 engraved side-by-side on an engraving line 32 for thegradation “dark” with the measuring band 39 aligned in the X-direction.

FIG. 8 shows the measurement of the web width (d_(SB)) of two samplecups 33 engraved on engraving lines 32 lying side-by-side with themeasuring band 39 aligned transverse relative to the engraving lines 32.

For enhancing the recognition and measuring dependability as well as formeasuring minimal or, respectively, maximal lengths and for measuringareas, measuring bands 39 having a plurality of measuring lines 39′ arepreferably employed.

The recognition and measuring dependability can be improved in that themeasured results of every measuring line 39′ are compared to one anotherand are only forwarded given coincidence. For determining maximum andminimum lengths, the measured results of the individual measuring line39′ are subjected to an extreme value selection. Given measurement ofthe transverse diagonal (d_(Q)) and of the longitudinal diagonal(d_(L)), a maximum selection is advantageously implemented and, aminimum selection is implemented given measurement of the web width(d_(SB)) and of the puncture (d_(DS)). For measuring a cup area, themeasured results of the individual measuring lines 39′ are added up.

For further improvement of the measuring dependability in anadvantageous development of the method, a defined measuring area 45 isadditionally placed around each sample cup 33 in the interpretation ofthe video image 35 whose maximum transverse diagonal (d_(Qmax)) orlongitudinal diagonal (d_(Lmax)) is measured, the size of said measuringarea at least corresponding to the cup area of the corresponding samplecup 33. The size of the measuring band 39 is adapted to the size of themeasuring area 45, so that all pixels 36 within the measuring area 45can be acquired by the measuring band 39.

The cup area of the corresponding sample cup 33 is then identified as aplurality of pixels 33 with the measuring band 39, in that the pluralityof pixels 36 counted in each measuring line 39 of the measuring band 39are added up.

The cup area of this sample cup 33 is then calculated from the maximumtransverse diagonal (d_(Qmax)) or longitudinal diagonal (d_(Lmax)) ofthe sample cup 33 measured with the measuring band 39. When nocoincidence is found between the calculated and the measured cup area ofthe sample cup 33, the measured result for the maximum transversediagonal (d_(Qmax)) or longitudinal diagonal (d_(Lmax)) of the samplecup 33 is annulled.

FIG. 9 shows a further video image 35 of engraved sample cups 33. Ameasuring area 45 is defined around the cup area of a sample cup 33 forthe gradation “light”. A correspondingly large measuring area 45″ isdefined around the cup area of a sample cup 33″ for the gradation“dark”. Alternatively, only a sub-measuring area of the measuring area45″ can also be utilized for measuring the cup area of the sample cup33″, for example a sub-measuring area 46 that corresponds to half themeasuring area 45″ or a sub-measuring area 47 that corresponds toone-fourth of the measuring area 45″. The entire cup area is thencalculated from the area parts identified in the individualsub-measuring area 46, 47, whereby it must be taken into considerationwhether it is a matter of symmetrical or asymmetrical surface parts withreference to the center of gravity of the area.

In another advantageous development of the method, the selectedreference cup or the reference location 41 in the video image 35 isautomatically identified on the basis of the characteristic quantity ofthe cup area of the selected reference cup.

For that purpose, the cup area of the selected reference cup isprescribed. The cup areas of all sample cups 33 are then identified inthe video image 35 by evaluation of the video data (VD) of theindividual pixels 36, and are respectively compared to the cup area ofthe selected reference cup. The reference cup and, thus, the referencelocation 41 is recognized when area coincidence is identified.

Alternatively, a recognition window can be defined that is smaller thanthe video image 35. In this case, the recognition window is shiftedstep-by-step over the video image 35, whereby a corresponding areacomparison is implemented in every window position.

Although various minor changes and modifications might be proposed bythose skilled in the art, it will be understood that my wish is toinclude within the claims of the patent warranted hereon all suchchanges and modifications as reasonably come within my contribution tothe art.

1. A method for producing and evaluating a sample cut in a electronicengraving machine for engraving printing forms for rotogravure,comprising the steps of: forming an engraving control signal for drivingthe engraving stylus of an engraving element from engraving data whichrepresent rated gradations between “light” and “dark” to be engraved andfrom a periodic raster signal for generating an engraving raster;providing a sample engraving before actual engraving of the printingform, wherein sample cups are engraved for predetermined ratedgradations; producing a video image of the sample cups engraved in thesample engraving; for measuring geometric parameters of the engravedsample cups, selecting an engraved sample cup in the video image for oneof the predetermined rated gradations as a reference location in anXY-measuring system allocated to the video image; dependent on theraster parameters of the engraving raster, defining measuring locationsfor measuring the geometric parameters of the sample cups in the videoimage as coordinate-related spacings from the selected referencelocation; measuring the geometric parameters of the sample cups at thedetermined measuring locations by interpreting the video image, andcomparing them to the geometric parameters that define the predeterminedrated gradations; deriving setting values from the comparison with whichthe engraving control signal is calibrated such that the engraved actualgradations correspond to the rated gradations to be engraved; with theengraving stylus engraving a sequence of cups arranged in the engravingraster engraving line by engraving line into the printing cylinder,geometric parameters of the cups defined engraved, actual gradations;and with the engraving element implementing a feed motion directed in anaxial direction of the printing cylinder for planar engraving of theprinting cylinder.
 2. The method according to claim 1 wherein samplecups for the rated gradations “light”, “dark” and at least one “midgradation” are engraved in the sample engraving.
 3. The method accordingto claim 1 wherein the sample cups for the rated gradations “light”,“dark” and “mid gradation” are respectively engraved on neighboringengraving lines.
 4. The method according to claim 1 wherein the samplecups are engraved over an engraving line region on each engraving line.5. A method for producing and evaluating a sample cut in a electronicengraving machine for engraving printing forms for rotogravure,comprising the steps of: forming an engraving control signal for drivingthe engraving stylus of an engraving element from engraving data whichrepresent rated gradations between “light” and “dark” to be engraved andfrom a periodic raster signal for generating an engraving raster;providing a sample engraving before actual engraving of the printingform, wherein sample cups are engraved for predetermined ratedgradations; producing a video image of the sample cups engraved in thesample engraving; for measuring geometric parameters of the engravedsample cups, selecting an engraved sample cup in the video image for oneof the predetermined rated gradations as a reference location in anXY-measuring system allocated to the video image; an area mid point ofan engraved sample cup being selected as the reference locationdependent on the raster parameters of the engraving raster, definingmeasuring locations for measuring the geometric parameters of the samplecups in the video image as coordinate-related spacings from the selectedreference location; measuring the geometric parameters of the samplecups at the determined measuring locations by interpreting the videoimage, and comparing them to the geometric parameters that define thepredetermined rated gradations; deriving setting values from thecomparison with which the engraving control signal is calibrated suchthat the engraved actual gradations correspond to the rated gradationsto be engraved; with the engraving stylus engraving a sequence of cupsarranged in the engraving raster engraving line by engraving line intothe printing cylinder, geometric parameters of the cups definingengraved, actual gradations; and with the engraving element implementinga feed motion directed in an axial direction of the printing cylinderfor planar engraving of the printing cylinder.
 6. The method accordingto claim 1 wherein an area mid point of an engraved sample cup for arated gradation “mid gradation” is selected as the reference location.7. The method according to claim 1 wherein the geometric parameters ofthe sample cups to be measured are at least one of transverse diagonal,longitudinal diagonal, punctures, web widths or cup areas of theengraved sample cups.
 8. The method according to claim 1 wherein thevideo image is divided into pixels; a measuring field displaceable overthe video image onto the defined measuring location is produced formeasuring the geometric parameters of the sample cups; the measuringfield comprises at least one measuring line with a plurality of pixelswhose spacings from one another represent length increments; theplurality of pixels of the measuring line devolving onto a measuringdistance in the video image are counted; and a length of the measuringdistance is determined as a multiple of the length increments.
 9. Themethod according to claim 8 wherein the measuring distance in the videoimage is defined by a spacing of two contours belonging to a sample cup.10. The method according to claim 9 wherein the contours of the samplecups are recognized by an automatic interpretation of the video image.11. The method according to claim 9 wherein the contours of the samplecups are recognized with at least one measuring line of the measuringband.
 12. A method for producing and evaluating a sample cut in aelectronic engraving machine for engraving printing forms forrotogravure, comprising the steps of: forming an engraving controlsignal for driving the engraving stylus of an engraving element fromengraving data which represent rated gradations between “light” and“dark” to be engraved and from a periodic raster signal for generatingan engraving raster; providing a sample engraving before actualengraving of the printing form, wherein sample cups are engraved forpredetermined rated gradations; producing a video image of the samplecups engraved in the sample engraving; for measuring geometricparameters of the engraved sample cups, selecting an engraved sample cupin the video image for one of the predetermined rated gradations as areference location in an XY-measuring system allocated to the videoimage; dependent on the raster parameters of the engraving raster,defining measuring locations for measuring the geometric parameters ofthe sample cups in the video image as coordinate-related spacings fromthe selected reference location, measuring the geometric parameters ofthe sample cups at the determined measuring locations by interpretingthe video image, and comparing them to the geometric parameters thatdefine the predetermined rated gradations; deriving setting values fromthe comparison with which the engraving control signal is calibratedsuch that the engraved actual gradations correspond to the ratedgradations to be engraved; with the engraving stylus engraving asequence of cups arranged in the engraving raster engraving line byengraving line into the printing cylinder, geometric parameters of thecups defining engraved, actual gradations; and with the engravingelement implementing a feed motion directed in an axial direction of theprinting cylinder for planar engraving of the printing cylinder; thevideo image is divided into pixels; a measuring field displaceable overthe video image onto the defined measuring location is produced formeasuring the geometric parameters of the sample cups; the measuringfield comprises at least one measuring line with a plurality of pixelswhose spacings from one another represent length increments; theplurality of pixels of the measuring line devolving onto a measuringdistance in the video image are counted; and a length of the measuringdistance is determined as a multiple of the length increments themeasuring distance in the video image being defined by a spacing of twocontours belonging to a same cup; each pixel of the video image having avideo datum allocated to it that identifies whether the correspondingpixel is a component part of a sample cup or not; the video data ofrespectively two successive pixels of the measuring line being examinedfor a modification; and an identified modification of the video databeing recognized as a contour.
 13. The method according to claim 12wherein the investigation of the video data for the recognition ofcontours of traverse diagonals and longitudinal diagonals occursproceeding from a middle to ends of the measuring line.
 14. The methodaccording to claim 12 wherein the investigation of the video data forthe recognition of the contours of puncture and web widths occurs fromends to a middle of the measuring line.
 15. The method according toclaim 8 wherein a mid point of the measuring field is defined as ameasuring location.
 16. The method according to claim 8 wherein thesample cup for “light”, “dark” and “mid gradation” respectively has aseparate measuring band allocated to it.
 17. A method for producing andevaluating a sample cut in a electronic engraving machine for engravingprinting forms for rotogravure, comprising the steps of: forming anengraving control signal for driving the engraving stylus of anengraving element from engraving data which represent rated gradationsbetween “light” and “dark” to be engraved and from a periodic rastersignal for generating an engraving raster; providing a sample engravingbefore actual engraving of the printing form, wherein sample cups areengraved for predetermined rated gradations; producing a video image ofthe sample cups engraved in the sample engraving; for measuringgeometric parameters of the engraved sample cups, selecting an engravedsample cup in the video image for one of the predetermined ratedgradations as a reference location in an XY-measuring system allocatedto the video image; dependent on the raster parameters of the engravingraster, defining measuring locations for measuring the geometricparameters of the sample cups in the video image as coordinate-relatedspacings from the selected reference location; measuring the geometricparameters of the sample cups at the determined measuring locations byinterpreting the video image, and comparing them to the geometricparameters that define the predetermined rated gradations; derivingsetting values from the comparison with which the engraving controlsignal is calibrated such that the engraved actual gradations correspondto the rated gradations to be engraved; with the engraving stylusengraving a sequence of cups arranged in the engraving raster engravingline by engraving line into the printing cylinder, geometric parametersof the cups defining engraved, actual gradations; and with the engravingelement implementing a feed motion direction in an axial direction ofthe printing cylinder for planar engraving of the printing cylinder; thevideo image is divided into pixels; a measuring field displaceable overthe video image onto the defined measuring location is produced formeasuring the geometric parameters of the sample cups; the measuringfield comprises at least one measuring line with a plurality of pixelswhose spacings from one another represent length increments; theplurality of pixels of the measuring line devolving onto a measuringdistance in the video image are counted; a length of the measuringdistance being determined as a multiple of the length increments; themeasuring field being formed as a stripe-shaped measuring band; and alongitudinal expanse of the measuring band amounting to at least aspacing of two engraving lines from one another.
 18. The methodaccording to claim 16 wherein the measuring band in a measuring locationhas its longitudinal expanse directed in an arbitrary direction withrespect to an XY measuring system.
 19. The method according to claim 16wherein the measuring band has its longitudinal expanse aligned in anX-direction of a measuring system which is a feed direction formeasuring transverse diagonal and puncture.
 20. The method according toclaim 16 wherein the measuring band has its longitudinal expanse alignedin a Y-direction of an XY measuring system which is a circumferentialdirection for measuring longitudinal diagonals.
 21. The method accordingto claim 16 wherein the measuring band has its longitudinal expansealigned transversely, to the path of the web for measuring web widths inXY measuring system.
 22. The method according to claim 16 wherein themeasuring band comprises a plurality of measuring lines arrangedparallel to one another; measured results achieved with the individualmeasuring lines are compared to one another; and the measured result ofa measuring line, for enhancing the measuring dependability, is onlyforwarded given coincidence of the measured results compared to oneanother.
 23. The method according to claim 16, wherein the measuringband comprises a plurality of measuring lines arranged parallel to oneanother; measured results achieved with the individual measuring linesare subjected to an extreme value selection; and only a highest orlowest measured result is forwarded.
 24. The method according to claim16 wherein the measuring band comprises a plurality of measuring linesarranged parallel to one another; measuring results achieved with theindividual measuring lines are added up for determining a size of anarea; and a sum is forwarded as measured result.
 25. The methodaccording to claim 16 wherein a maximum transverse diagonal orlongitudinal diagonal of a sample cup is measured with the measuringband; the cup area of the corresponding sample cup is calculated fromthe measured, maximum transverse diagonal or longitudinal diagonal; thecup area of the corresponding sample cup is measured with the measuringband; the measured and the calculated cup area are compared to oneanother; and the measured result for the maximum transverse diagonal orlongitudinal diagonal is forwarded only given coincidence of measuredand calculated cup area.
 26. The method according to claim 1 wherein thesample cup, which should be the reference location, is automaticallyidentified in the video image.
 27. The method according to claim 1wherein a cup area of the sample cup selected as the reference locationis prescribed; cup areas of all sample cups are identified in the videoimage on the basis of video data; the identified cup areas of the samplecups are compared to the predetermined cup area; and that sample cupwhose measured cup area coincides with the predetermined cup area ismarked as the reference location.
 28. A method for producing andevaluating a sample cut in an electronic engraving machine, comprisingthe steps of: forming an engraving control signal for driving anengraving element from engraving data, which represent rated gradationsbetween “light” and “dark” to be engraved and from a periodic rastersignal for generating an engraving raster; providing a sample engravingbefore actual engraving wherein sample cups are engraved forpredetermined rated gradations; producing a video image of the samplecups engraved in the sample engraving; for measuring geometricparameters of the engraved sample cups, selecting an engraved sample cupin the video image for one of the predetermined rated gradations as areference location in a system allocated to the video image; dependenton the raster parameters of the engraving raster, defining measuringlocations for measuring geometric parameters of the sample cups in thevideo image as coordinate-related spacings from the selected referencelocation; measuring the geometric parameters of the sample cups at thedetermined measuring locations by interpreting the video image, andcomparing them to the geometric parameters that define the predeterminedrate gradations; and deriving setting values from the comparison withwhich the engraving control signal is calibrated such that the engravedactual gradations correspond to the rated gradations to be engraved; andengraving cups with the engraving element.